efi: libstub: fix efi_load_initrd_dev_path() kernel-doc comment

commit f4dc7fff

 ("efi: libstub: unify initrd loading between
architectures") merge the first and the second parameters into a
struct without updating the kernel-doc. Let's fix it.

Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>